by B.B. Pelletier
On Friday, we received a comment with several questions that I’d like to address this week. The first concerns selecting the correct pellets for the Diana RWS 52. I’ll talk you through that and generalize for most springers – so you’ll be able to pick great pellets on your own. The comment we received included the following, “…could you offer an explanation as to why some pellets are seemingly more accurate than others? And I am using heavy weight pellets, could you comment on the value of using heavy vs lighter ones in this air rifle?
Heavy vs light pellets
In a spring gun, the piston travels all the way forward and comes to a stop before the pellet starts to move (that’s the way it’s supposed to work). If you use a very light or very loose-fitting pellet, the pellet can start to move before the piston stops. When the piston comes to a stop, it does so against a thin cushion of highly compressed air that separates it from the front of the compression chamber. That cushion protects the piston seal from impact damage. Sometimes, the piston will rebound off this high-pressure air cushion just as the pellet starts to move forward. If it bounces too far, it will lower the air pressure and rob the shot of potential power.
From the standpoint of efficiency only (accuracy not considered), the best pellet for a particular spring gun is one that starts to move at the moment the piston comes to a stop. That allows the piston to settle softly against the end of the compression chamber as the air pressure drops. Now, how do you determine which pellet that is?
You use a chronograph to determine which pellets give the greatest power in your gun. We’ve discussed this before, and you now know that spring guns favor lighter pellets (this is the reason why). Light pellets work better because they start moving sooner. Springers like that because they don’t have a large amount of compressed air to work with. Are only light pellets good for springers? NOT AT ALL!
You must consider accuracy!
Power without accuracy is a waste of time. The goal is to combine the best accuracy with the best power in a given gun. A short-stroke action like one of the RWS sidelevers tends to extract more power from the lightest pellets, while a long-stroke action like the Diana RWS 350 Magnum probably likes pellets in the medium-weight range. Try them also for accuracy to find the absolute best pellet. While 7.0-grain RWS Hobby pellets may give the most power in a .177 RWS 52, it may be that 10.5-grain Crosman Premiers are more accurate. Shoot the heavy Premiers and forget the 1.5 to 2 foot-pounds of greater power the Hobbys might deliver in that rifle.
Incidentally, a Diana RWS 52 in .177 is capable of sub-1″ five-shot groups at 50 yards. At 35 yards, a good shooter should be almost able to keep all his shots on a dime. That’s shooting on a calm day from a rest and resting the forearm on the flat of your open hand. Your trigger-finger hand does not hold the pistol grip any tighter than necessary, and the butt is not pulled into your shoulder. If there’s a scope level on the rifle, check it before each shot. If you grasp the rifle’s stock in any way, you can forget that level of accuracy.
Can the wrong pellet damage the rifle?
There isn’t much information on this subject, but I believe the wrong pellet can injure a spring rifle. I think shooting a pellet that is either too light or too loose is similar to dry-firing the gun. I know Gamo says their guns can take it, but I still do not like doing it. Very light/very loose pellets can also cause explosive detonations, and we are pretty sure they do damage the mainsprings. Diana RWS guns have very hard mainsprings (maybe a touch too hard), and they’re most susceptible to damage caused by detonations. I have fixed several Diana RWS guns that had one inch broken off at one or both ends of the spring. Those guns will keep right on shooting, but they show a distinct drop in velocity.
What about real heavy pellets?
Some people feel heavy pellets also damage mainsprings. I don’t believe this myself, but as I said, there isn’t much to go on. Another problem with pellets that are too heavy is that they don’t stabilize well enough for good accuracy at longer ranges (beyond 40 yards).
Do I have to test EVERY pellet to find a good one?
No! I addressed this on several occasions in past postings, but the best one is Best pellet of all? posted on August 19, 2005. Read that and also use the Bloglines search engine on this blog to look for other pellet postings. Testing every pellet is a waste of time and money, since many of them don’t work well in ANY airgun. I also have a rule of thumb that I follow: RWS airgun, RWS pellet. Do that for all manufacturers; it works a lot of the time.
Here is what I have not answered with this posting: Why some pellets are more accurate than others. I wish I knew the answer, but I don’t. I also don’t trust anyone who says they do. I do know that pellets that have been sorted by weight usually out-perform those that haven’t been, and JSB pellets are all hand-sorted. That’s why I believe JSBs are often the most accurate pellets.